The thing about anime is you have to find someone whose opinion and taste aligns with your own so you suggest stuff each other and feed off one another. It's a lot like being a music fan. You have to dig deep and research to find good shit. And then your friend who is looking out suggests something you would love and you to them. It becomes a back and forth.
The problem is that when that friend stops watching you're now left with no ones taste to trust. And without someone's taste to trust you have to rely on the average anime fan, who generally have shit taste in anime, just like how the average music listener has shit taste in music. The positive with music is that it's less time consuming than anime. You can listen to an album of average length in an hour. An anime is 24 minutes per episode and can be be long, and are aired weekly. It takes 4-5 episodes to usually see if an anime is for you, which, if it's airing currently, is five weeks. Ain't no one got time for that without a buffer to help tell you what's good when everyone around you has shit taste.
So you stop watching because it's no longer a rewarding or interesting hobby.
For the record, my taste in anime is pretty good and this has been my experience.